Which interrail timetable ? Yes Rail Planner is a bit unreliable but you should find the trains. They'll first show the fast connections with mandatory reservations but you can deselect those.
Unfortunately this Eurostar doesn't stop in Lille so you'll have to go all the way to Brussels. Don't worry the journey will only be a bit longer.
Option 1 :
- IC Bruxelles-Midi - Tournai 10:13 - 11:15
- IC Tournai - Lille-Flandres 11:22 - 11:52
- TGV Lille-Europe (5 min walk) - Paris-Nord 13:03 - 14:32 10€ per person
There are also multiple later TGVs from Lille-Europe or Lille-Flandres if you'd like to make a stop there. You could also visit Brussels for a bit (hourly trains). By regional train from Lille :
- TER Lille-Flandres - Amiens 12:53 - 14:12
- TER Amiens - Paris-Nord 14:38 - 15:56
Option 2 :
- spend a few hours in Brussels
- IC Bruxelles-Midi - Charleroi-Central 13:15 - 14:07
- R Charleroi-Central - Maubeuge 14:24 - 15:20
- TER Maubeuge - Paris-Nord 15:42 - 17:41
Other departures at 09:15 (too tight) or 15:15.
A third option would be to take a ferry instead (but I don't think Eurostar could get refunded). It's not faster anyway.
Do not hesitate for questions.